Tag: Heads

We have Heads tamper-evident boot working on Librem laptops and I'm using it daily! Check out my write up where I explain how it + the rest of our features makes Librems the most secure laptop you can buy where you hold the keys. #infosec#coreboothttps://t.co/CeiaZaHBj7

The UEFI Forum likes to frame UEFI -vs- BIOS, and has a 3-5 Class heirarchy of those systems, including having to deal with UEFI systems that also provide BIOS via Compatibility Support Module (CSM), referring to BIOS as Legacy Mode. If you look at BIOS outside of the framing of the UEFI Forum, it is usually based security, and UEFI has some security where BIOS has none. But there’s another ‘class’: non-UEFI coreboot, optionally secured with Verified Boot, with a BIOS payload. UEFI Forum doesn’t include this in their Class heirarchy… AFAICT, the mainstream IBVs have given up on BIOS and migrated to UEFI. The only places where BIOS will probably remain are in Purism boxes, where they will use TPM+Heads to secure BIOS, or on Chrome boxes, where they will use coreboot Verified Boot to secure BIOS, or in SeaBIOS-based VMs. When Intel stops offering Intel’s implementation of BIOS, maybe this means that the remaining BIOS users will switch to the open source SeaBIOS project, which is great news. Getting rid of the complex class of dual UEFI/BIOS systems will be a joy. 🙂

that Purism is getting ready to start using Heads payload. They’ve been talking about it for months, maybe it’ll be a real option for upcoming Librem customers? I’m very excited to see a Heads system available by an OEM, instead of DIY and not an easy task.

And they’re adding a TPM as an ‘add-on’ to existing Librem laptops. Heads needs TPM for it’s measurements. (Hmm, I thought TPMs were an integral and tamper-resistant part of the system, and something that could be added on for trust was called a smartcard, but ok. I guess you have to solder the HW to the system. I presume attackers will be ordering spare add-ons so they can swap out units.)

In the above Purism forum, there was this user comment:

“I like the idea of putting a demo Librem notebook to a BlackHat conf where they try to break into the devices. Would be a nice test and a good commercial for you.”

They cannot do that with current Librem models. 🙂 This will need to wait for TPMs to be pre-installed and Heads as the payload.

This response from the above Purism forum seems a bit invalid:

“So there’s no way to access a BIOS menu to change the boot sequence (boot from USB) or set a machine password etc?”

“No, there is no such thing. The BIOS boots into your machine in roughly 450 milliseconds, there is no support for a menu, there is no time even for the user to press a key on the keyboard to enter a menu. The idea of coreboot is to do the minimum hardware initialization and then go to a payload. In our case, we use SeaBIOS which itself will initialize the video card and show the splash screen logo, and wait for 2 seconds for you to press ESC to show you the boot menu and let you choose your device (otherwise, it just boots to the default one). The boot choice isn’t saved, it’s just a boot override. If you want to change an option in coreboot, you need to change the config in the source and recompile coreboot then reflash it. If you want to change the boot order, you need to change the boot order in a file embeded in the flash, then reflash the BIOS.”

Yes, there is thing, which the reply says does not exist then a few sentences later explains that it does exist. The BIOS menu to change the boot order is available to anyone with physical access to the system, and presses the ESC key within 2 seconds of poweron. The unprotected BIOS and MBR-based hard drive can be quickly overwritten with malware on the attacker’s boot thumbdrive. Attendees of ‘a BlackHat conf’ will have such skills. 🙂

Purism is spending all their time undoing Intel’s features — Intel ME, Intel FSP, and now re-embracing older features — Intel TPM. Intel SMM is still an issue, STM is not being used by Purism. Intel ME may be disabled, but it’s a black-box device, who knows when attackers will start reactivating it and putting their malware-based version of Minix on that chip? You’re going to need tools to detect if ME is really disabled. I hope Purism’s roadmap has a RISC-V chip-based laptop in it, so they can stop fighting Intel features and have a fully-open stack. If they keep fighting the Intel stack, I hope they add the ‘stateless laptop’ that Joanna has proposed to their roadmap:

It might be useful to add coreboot Verified Boot to help secure their SeaBIOS payload, but that could probably only secure PureOS, and distro hoppers will have no benefit. But I don’t think Heads and Verified Boot are compatible? SeaBIOS also has TPM support, that’d be nice to see those measurements used, if they are embracing a TPM. And now that they have a TPM, they can start using Intel TXT too. 🙂

I am a little perplexed about Purims customer audience, who is concerned about privacy, and yet has so little concern for security, in exchange for the convenience feature of being easy to distro-hop. Anyway, if you want security, wait for the TPM and Heads to be integrated with future Librems.

The 33rd Chaos Communication Congress (CCC) takes place in December in Germany. There are MANY great presentations, and CCC is great at making video archives available. Here’s a sample of a few of the presentations, starting with Trammell’s lecture on Heads:

Heads is a very interesting new distro by Trammel Hudson. If you like Qubes or Subgraph or Tails, read about this new distro.

The threat model that Heads proposes to address is very different from that of Tails. Tails’s goal is to allow users to to do computation on a machine in a way that doesn’t leave in trace on that system. This requires that the hardware in the system is trusted, which unfortunately is not the case for many users. Additionally many users need a way to keep state in a permanent way and don’t want to expose this state to random machines. Their machines might be subject to physical attacks that might install untrusted firmware or other devices into the system.[1][2] For these reasons, Tails is not sufficient for many users who want a laptop that they can travel with and want to have some assurances that most adversaries won’t be able to modify the hardware underneath them. Complicating this goal is that modern x86 hardware is full of modifiable state[3] and it is full of dusty corners that can hide malware or unauthorized code. Additionally there is unverifable code running in the Intel Management Engine, which has access to memory, to the network and various other peripherals. As a result we must trust certain entities more than others and this does affect our threat model. This document discusses some of the threats that make building slightly more secure mobile systems very difficult. There is a separate guide on installing Heads on the Thinkpad x230, which covers the practical issues of hardening a laptop against some of the threats described here. […]”